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<article id="content">
<header>
<h1 class="title">Module <code>wasi</code></h1>
</header>
<section id="section-intro">
<p>Wasmer's <a href="https://github.com/WebAssembly/WASI">WASI</a>
implementation.</p>
<p>From the user perspective, WASI is a bunch of imports. To generate
the appropriated imports, you can use <code><a title="wasi.StateBuilder" href="#wasi.StateBuilder">StateBuilder</a></code> to build an
<code><a title="wasi.Environment" href="#wasi.Environment">Environment</a></code>. This environment holds the WASI memory, and can be
used to generate a valid <code><a title="wasmer.ImportObject" href="../wasmer/index.html#wasmer.ImportObject">ImportObject</a></code>. This last one can
be passed to <code><a title="wasmer.Instance" href="../wasmer/index.html#wasmer.Instance">Instance</a></code> to instantiate a <code><a title="wasmer.Module" href="../wasmer/index.html#wasmer.Module">Module</a></code>
that needs WASI support.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi, Store, Module, Instance

store = Store()
module = Module(store, open('tests/wasi.wasm', 'rb').read())

# Get the WASI version.
wasi_version = wasi.get_version(module, strict=True)

# Build a WASI environment for the imports.
wasi_env = wasi.StateBuilder('test-program').argument('--foo').finalize()

# Generate an `ImportObject` from the WASI environment.
import_object = wasi_env.generate_import_object(store, wasi_version)

# Now we are ready to instantiate the module.
instance = Instance(module, import_object)

# … But (!) WASI needs an access to the memory of the
# module. Simple, pass it.
wasi_env.memory = instance.exports.memory

# Here we go, let's start the program.
instance.exports._start()
</code></pre>
</section>
<section>
</section>
<section>
</section>
<section>
<h2 class="section-title" id="header-functions">Functions</h2>
<dl>
<dt id="wasi.get_version"><code class="name flex">
<span>def <span class="ident">get_version</span></span>(<span>module, strict)</span>
</code></dt>
<dd>
<div class="desc"><p>Detect the version of WASI being used based on the import
namespaces.</p>
<p>A strict detection expects that all imports live in a single WASI
namespace. A non-strict detection expects that at least one WASI
namespace exits to detect the version. Note that the strict
detection is faster than the non-strict one.</p></div>
</dd>
</dl>
</section>
<section>
<h2 class="section-title" id="header-classes">Classes</h2>
<dl>
<dt id="wasi.Environment"><code class="flex name class">
<span>class <span class="ident">Environment</span></span>
</code></dt>
<dd>
<div class="desc"><p>The environment provided to the WASI imports.</p>
<p>To build it, use <code><a title="wasi.StateBuilder" href="#wasi.StateBuilder">StateBuilder</a></code>. See <code><a title="wasi.StateBuilder.finalize" href="#wasi.StateBuilder.finalize">StateBuilder.finalize()</a></code> to
learn more.</p></div>
<h3>Instance variables</h3>
<dl>
<dt id="wasi.Environment.memory"><code class="name">var <span class="ident">memory</span></code></dt>
<dd>
<div class="desc"><p>Set a memory to the WASI. Usually, it is a <code><a title="wasmer.Memory" href="../wasmer/index.html#wasmer.Memory">Memory</a></code>
object from <code>instance.exports.&lt;memory_name&gt;</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi, Store, Module, Instance

store = Store()
module = Module(store, open('tests/wasi.wasm', 'rb').read())

# Get the WASI version.
wasi_version = wasi.get_version(module, strict=True)

# Build a WASI environment for the imports.
wasi_env = wasi.StateBuilder('test-program').argument('--foo').finalize()

# Generate an `ImportObject` from the WASI environment.
import_object = wasi_env.generate_import_object(store, wasi_version)

# Now we are ready to instantiate the module.
instance = Instance(module, import_object)

# … But (!) WASI needs an access to the memory of the
# module. Simple, pass it.
wasi_env.memory = instance.exports.memory

# Here we go, let's start the program.
instance.exports._start()
</code></pre></div>
</dd>
</dl>
<h3>Methods</h3>
<dl>
<dt id="wasi.Environment.generate_import_object"><code class="name flex">
<span>def <span class="ident">generate_import_object</span></span>(<span>...)</span>
</code></dt>
<dd>
<div class="desc"><p>Create an <code><a title="wasmer.ImportObject" href="../wasmer/index.html#wasmer.ImportObject">ImportObject</a></code> with an existing
<code><a title="wasi.Environment" href="#wasi.Environment">Environment</a></code>. The import object will be different according
to the WASI version.</p>
<p>Use the <code><a title="wasi.Version" href="#wasi.Version">Version</a></code> enum to use a specific WASI version, or use
<code><a title="wasi.get_version" href="#wasi.get_version">get_version()</a></code> to read the WASI version from a <code><a title="wasmer.Module" href="../wasmer/index.html#wasmer.Module">Module</a></code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi, Store

store = Store()
wasi_env = wasi.StateBuilder('test-program').argument('--foo')
import_object = wasi_env.generate_import_object(store, wasi.Version.SNAPSHOT1)
</code></pre></div>
</dd>
</dl>
</dd>
<dt id="wasi.StateBuilder"><code class="flex name class">
<span>class <span class="ident">StateBuilder</span></span>
<span>(</span><span>arguments=[], environments={}, preopen_directories=[], map_directories={})</span>
</code></dt>
<dd>
<div class="desc"><p>Convenient builder API for configuring WASI.</p>
<p>Use the constructor to pass the arguments, environments, preopen
directories and map directories, or use the associated methods to
build the state step-by-steps.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = wasi.StateBuilder('test-program')
</code></pre></div>
<h3>Methods</h3>
<dl>
<dt id="wasi.StateBuilder.argument"><code class="name flex">
<span>def <span class="ident">argument</span></span>(<span>self, /, argument)</span>
</code></dt>
<dd>
<div class="desc"><p>Add an argument.</p>
<p>Arguments must not contain the nul (<code>0x0</code>) byte.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        argument('--verbose'). \
        argument('--help')
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.arguments"><code class="name flex">
<span>def <span class="ident">arguments</span></span>(<span>self, /, arguments)</span>
</code></dt>
<dd>
<div class="desc"><p>Add multiple arguments.</p>
<p>Arguments must not contain the nul (<code>0x0</code>) byte.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        arguments(['--verbose --help'])
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.environment"><code class="name flex">
<span>def <span class="ident">environment</span></span>(<span>self, /, key, value)</span>
</code></dt>
<dd>
<div class="desc"><p>Add an environment variable pair.</p>
<p>Environment variable keys and values must not contain the byte
<code>=</code> (<code>0x3d</code>) or null (<code>0x0</code>).</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        environment(&quot;ABC&quot;, &quot;DEF&quot;). \
        environment(&quot;X&quot;, &quot;YZ&quot;)
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.environments"><code class="name flex">
<span>def <span class="ident">environments</span></span>(<span>self, /, environments)</span>
</code></dt>
<dd>
<div class="desc"><p>Add environment variable pairs.</p>
<p>Environment variable keys and values must not contain the byte
<code>=</code> (<code>0x3d</code>) or null (<code>0x0</code>).</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        environments({&quot;ABC&quot;: &quot;DEF&quot;, &quot;X&quot;: &quot;YZ&quot;})
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.finalize"><code class="name flex">
<span>def <span class="ident">finalize</span></span>(<span>self, /)</span>
</code></dt>
<dd>
<div class="desc"><p>Produces a WASI <code><a title="wasi.Environment" href="#wasi.Environment">Environment</a></code> based on this state builder.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_env = \
    wasi.StateBuilder('test-program'). \
        argument('--foo'). \
        finalize()
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.map_directories"><code class="name flex">
<span>def <span class="ident">map_directories</span></span>(<span>self, /, map_directories)</span>
</code></dt>
<dd>
<div class="desc"><p>Preopen directories with different names exposed to the WASI.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        map_directories({&quot;foo&quot;: &quot;.&quot;})
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.map_directory"><code class="name flex">
<span>def <span class="ident">map_directory</span></span>(<span>self, /, alias, directory)</span>
</code></dt>
<dd>
<div class="desc"><p>Preopen a directory with a different name exposed to the WASI.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        map_directory(&quot;foo&quot;, &quot;.&quot;)
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.preopen_directories"><code class="name flex">
<span>def <span class="ident">preopen_directories</span></span>(<span>self, /, preopen_directories)</span>
</code></dt>
<dd>
<div class="desc"><p>Preopen directories.</p>
<p>This opens the given directories at the virtual root, <code>/</code>, and
allows the WASI module to read and write to the given
directories.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        preopen_directories([&quot;foo&quot;, &quot;bar&quot;])
</code></pre></div>
</dd>
<dt id="wasi.StateBuilder.preopen_directory"><code class="name flex">
<span>def <span class="ident">preopen_directory</span></span>(<span>self, /, preopen_directory)</span>
</code></dt>
<dd>
<div class="desc"><p>Preopen a directory.</p>
<p>This opens the given directory at the virtual root, <code>/</code>, and
allows the WASI module to read and write to the given
directory.</p>
<p>This method returns <code>self</code>.</p>
<h2 id="example">Example</h2>
<pre><code class="language-py">from wasmer import wasi

wasi_state_builder = \
    wasi.StateBuilder('test-program'). \
        preopen_directory(&quot;foo&quot;). \
        preopen_directory(&quot;bar&quot;)
</code></pre></div>
</dd>
</dl>
</dd>
<dt id="wasi.Version"><code class="flex name class">
<span>class <span class="ident">Version</span></span>
<span>(</span><span>value, names=None, *, module=None, qualname=None, type=None, start=1)</span>
</code></dt>
<dd>
<div class="desc"><p>An enumeration.</p></div>
<h3>Ancestors</h3>
<ul class="hlist">
<li>enum.IntEnum</li>
<li>builtins.int</li>
<li>enum.Enum</li>
</ul>
<h3>Class variables</h3>
<dl>
<dt id="wasi.Version.LATEST"><code class="name">var <span class="ident">LATEST</span></code></dt>
<dd>
<div class="desc"></div>
</dd>
<dt id="wasi.Version.SNAPSHOT0"><code class="name">var <span class="ident">SNAPSHOT0</span></code></dt>
<dd>
<div class="desc"></div>
</dd>
<dt id="wasi.Version.SNAPSHOT1"><code class="name">var <span class="ident">SNAPSHOT1</span></code></dt>
<dd>
<div class="desc"></div>
</dd>
</dl>
</dd>
</dl>
</section>
</article>
<nav id="sidebar">
<h1>Index</h1>
<div class="toc">
<ul>
<li><a href="#example">Example</a></li>
</ul>
</div>
<ul id="index">
<li><h3>Super-module</h3>
<ul>
<li><code><a title="wasmer" href="../wasmer/index.html">wasmer</a></code></li>
</ul>
</li>
<li><h3><a href="#header-functions">Functions</a></h3>
<ul class="">
<li><code><a title="wasi.get_version" href="#wasi.get_version">get_version</a></code></li>
</ul>
</li>
<li><h3><a href="#header-classes">Classes</a></h3>
<ul>
<li>
<h4><code><a title="wasi.Environment" href="#wasi.Environment">Environment</a></code></h4>
<ul class="">
<li><code><a title="wasi.Environment.generate_import_object" href="#wasi.Environment.generate_import_object">generate_import_object</a></code></li>
<li><code><a title="wasi.Environment.memory" href="#wasi.Environment.memory">memory</a></code></li>
</ul>
</li>
<li>
<h4><code><a title="wasi.StateBuilder" href="#wasi.StateBuilder">StateBuilder</a></code></h4>
<ul class="two-column">
<li><code><a title="wasi.StateBuilder.argument" href="#wasi.StateBuilder.argument">argument</a></code></li>
<li><code><a title="wasi.StateBuilder.arguments" href="#wasi.StateBuilder.arguments">arguments</a></code></li>
<li><code><a title="wasi.StateBuilder.environment" href="#wasi.StateBuilder.environment">environment</a></code></li>
<li><code><a title="wasi.StateBuilder.environments" href="#wasi.StateBuilder.environments">environments</a></code></li>
<li><code><a title="wasi.StateBuilder.finalize" href="#wasi.StateBuilder.finalize">finalize</a></code></li>
<li><code><a title="wasi.StateBuilder.map_directories" href="#wasi.StateBuilder.map_directories">map_directories</a></code></li>
<li><code><a title="wasi.StateBuilder.map_directory" href="#wasi.StateBuilder.map_directory">map_directory</a></code></li>
<li><code><a title="wasi.StateBuilder.preopen_directories" href="#wasi.StateBuilder.preopen_directories">preopen_directories</a></code></li>
<li><code><a title="wasi.StateBuilder.preopen_directory" href="#wasi.StateBuilder.preopen_directory">preopen_directory</a></code></li>
</ul>
</li>
<li>
<h4><code><a title="wasi.Version" href="#wasi.Version">Version</a></code></h4>
<ul class="">
<li><code><a title="wasi.Version.LATEST" href="#wasi.Version.LATEST">LATEST</a></code></li>
<li><code><a title="wasi.Version.SNAPSHOT0" href="#wasi.Version.SNAPSHOT0">SNAPSHOT0</a></code></li>
<li><code><a title="wasi.Version.SNAPSHOT1" href="#wasi.Version.SNAPSHOT1">SNAPSHOT1</a></code></li>
</ul>
</li>
</ul>
</li>
</ul>
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